Frustrated

I noticed a new account - Nimble - on my credit profile. I've contacted them on numerous occasions to try and pay this account and have it closed but every time I'm told that the account has been sold to CSF. Contacted CSF and they have no records for me. Why are you guys making thing so difficult for me when all I am trying to do is the right thing. I'm not disputing the amount owed, I just want to settle the account so that it can stop affecting my credit record. CSF doesn't show on my credit record, Nimble does. Provide me with the details of payment for this account or if you can't, remove it from my credit profile.